Plaster and method of making the same



Patented Feb. 17, 1931 v UNITED STATES ixamia PATENT OFFICE FOSTER DEE SNELL, OF BROOKLYN, NEW YORK PLASTER AND METHOD OF MAKING THE SAME No Drawing.

This invention relates to plasters and processes of making the same, and it comprises a plaster containing as usual a calcareous '0" 0 binder and an a ie ate and also contain lTgan intimately incorporated lime soap in minor amoun suc 1 amoun emg a out, but not substantially greater than, that which can be absorbed by the pore-forming surfaces of the solids in the plaster, this amount usually being of the ordeg of 0.002 to 0.01 per cent of the whole compositlon an eing su clent to reduce suction or speed of adsorption of vplater without substantial interference with t e oros1t an it further com rises a method of reducing the suction of plaster compositions without disturbing their porosity which comprises intermingling a soap with the plaster composition" at the time of gaging, the soap being used in the amount 29 which will produce sufficient lime soap to ive an adsorbed-coating thereof on the poreorming solid surfaces in the plaster without substantial plugging of pores, this amount being usually of the order of 0.002 to 0.01

, per cent of the whole compositlon; all as more fully hereinafter set forth and as claimed.

Wall plaster is composed of a calcareous binder, an aggregate (sand) and water the 30 amount of water being suflicient to give a troweling consistency and to give ahighly porous composition after the composltion is dry. Porosity in plaster is desirable. The

calcareous binder ma be lime cement alumlnate cement or laster of Pans. Plaster sa es.

. First, a scratch coat may be applied; second,

a brown coat; and finally, a finishing white coat. A typical brown coat composltion 1n the wet state carries :1 out 2 0 ounds of lime gand ma nesia}, 2500 ound s of sand and oun s 0 water er cublc yard; a total of 3&0 pounds. It may carry a pound or so of hair. Scratch coat com ositions usually 0 oun s.

5 carr more Eair, s

After the rown coat 15 applied it is given time to set up and dry out and then the final or finishing coat is applied. These operations require considerable sk ll. As stated, k the dry plaster should be qulte porous and Application filed. March 30, 1929. Serial No. 351,461.

set in the allotted time; and it is considered undesirable in the best practice to load the plaster with anything that will plug the pores. Much of the necessity for skill is because of the tendency of the suction of the partly dry set brown coat to abstract water from the white coat.

It is an object of the present invention to reduce the suction of dried or partially dried set plaster to a point where it does not interfere with the application of the finish coat; i. e. to a point where absorption of water is not inconveniently rapid; and to do this without plugging the pores, distributing the set or in any way interfering with the ordinary properties or manipulation of plaster.

Setting and drying of the plaster in place go on simultaneously, but drying is a variable factor depending on temperature and weather. The suction depends on the dryness, but is a quite irregular phenomenon. It is the irregularity in drying and in suction that necessitates special skill on the part of the plasterer.

In a general way, adsorption of water by the walls of a pore must precede absorption of water by the pore; a principle which is utilized in shower proofing garments. In partly dry plaster, adsorbed water films on the pore walls are still in place and absorption is rapid. Both the sand and the lime, but particularly the lime, have hygroscopic surfaces and retain this water film with considerable tenacity.

I have found that by producing a minute amount of colloidall dis ersed lime soa in the plaster, By an addition of'soam e soap is adsorbed on the surfaces of the solids and when the plaster sets to a porous layer, water no longer tends to enter rapidly. The lime soa s are uite non-h drosco ic and their presence on the pore walls reduces, or practically nullifies, the initial adsorption of water which is precedent to absorption. To secure the result that I want, namely reduction of suction without interference with porosity or any of the normal properties of the plaster, the amount of soap I use must be quite small; ordinarily not over 0.16 pounds per cubic yard of wet plaster. It is an interesting calculation that the amount of lime soap which is produced corresponds pretty nearly to a monomolecular film of soap covering the available solid surfaces in the plas- 5 ter with the amount of surface ordinarily present; that is, with materials in the ordinary state of subdivision. Perhaps there is a little less soap than corresponds to the entire surface available. About 0.35 ounds of soa such as soda soa er cubic yard is peraps the maximum or my purposes.

The particular nature of the lime soap which is present is not as important as its quantity. Suitable li eg scags for my puroses may be made by incorporating directly into the wet plaster mix any ordinary soap containin f acids or resin acids in conibination wit so a a or ammonia. e soaps reac wit t e 1me o orm 1me soa s. The same reaction occurs when the added soap, s y 0.16 pound. This soap is thoroughly incorporated with the mixture during the mixing of the putty and the sand. The result is a cubic yard of plaster ready for application to the wall. The desired amount of hair may be admixed with the composition.

In making plasters with cement or plaster of Paris, the procedure is similar and in general the proportions may be the same.

What claim is- 1. As a new material, a plaster of retarded suction, said plaster being composed of a calcareous binder, a filler and Water with a soap is mixed with wet lime, cement and minimal amount of included dispersed lime lasterof'Paris.

Ks stated, the amount of lime soap present is apparently about that which will be adsorbed by the solids with the production of a monomolecular film and it is not enough to produce any substantial plugging of pores. Uniform distribution of the lime soap throughout the mass, in spite of its small amount, offers no great difficulty. Ordinary mixing suflices.

By the means described a wet plaster can be produced which trowels, dries and otherwise behaves like ordinary plaster. No difference is observed by the workman in applying it to the wall. On the wall, it dries and sets in the ordinary fashion and the one difference is reduction of suction. WVater on a pat of the dried treated plaster is not taken up swiftly as it is by a similar pat of similar age of untreated plaster.

Suction is not entirely eliminated, nor is it desirable that it should be. The first plaster must take up enough of the next to permit 45 keying and bonding. By the use of about 0.16 pound of soap per cubic yard, the most advantageous results are obtained. With substantial increase i n the amount, the material becomes, in general, disadvantageously waterproof. For example, ,withan amount as great as 0.35 pound of soap per cubic yard,

the set plaster is almost too waterproof.

Such a proportion, however, is sometimes advantageous, as when it is desirable to finish the rou h coat with varnishes or oily compo-' soap, said soap being present in amounts not greater than 0.35 pound per cubic yard.

2. As a new material, a plaster of retarded suction, said plaster being composed of a calcareous binder, a filler and water with a minimal amount of included dispersed lime soap, said soap being present in amount of the or der of 0.16 pound per cubic yard.

3. As a new material, a wall plaster of retarded suction, said plaster being composed of lime, filler and water with a minimal amount of dispersed adsorbed lime soap, said soap being present in amounts of the order of about 0.16 pound per cubic yard.

4. The process of retarding the suction of wall plaster which comprises adding to the wetdplaster about 0.16 pound soap per cubic yar y 5. As a new material, a porous wall plaster o f retarded suction composed of a calcareous binder, a filler and Water and containing soap in amounts between 0.002 and 0.01 per cent of the whole mass.

6. As a new material, a calcareous wall plaster adapted to serve as a first or rough coat in plastering, said plaster containing a signature.

FOSTER DEE SNELL.

sitions in lieu of using a white coat of calcareous material. While lime soaps do not adsorb water readily, they do adsorb oily materials;'and with lime soap present in the 60 set paster, oily varnishes, lacquers and the like can be made to key to the set plaster prior to its complete drying.

In a specific embodiment of the present invention, roviding a ready mixed lime plaster of retar ed suction, pounds of lime are 

